Sperm Donation: If the man cannot provide sperm, the couple can use a sperm bank. The sperm are put into the vagina via a catheter, and make their way up to the oviducts. The donor, often a medical student, is anonymous. This method is called Artificial Insemination by a Donor (AID).

Egg Donation: If the woman cannot provide eggs, the couple can seek an egg donated by a third person. This person may be a close friend of the couple, or a stranger. Her retrieved egg is placed in a culture dish, and there fertilized by the partner's sperm. The embryo is then put into the woman's uterus or tubes.

Embryo Donation: If neither egg nor sperm can be provided, the couple can seek help from a third woman and man. The woman donates her egg, and the man his sperm. These are retrieved and fertilized in a culture dish, and the embryo is transplanted into the woman.

Uterus Donation: A mother "loaned" her uterus to her daughter and became the first grandmother to bear her own children. The daughter had been born without a uterus, but she could provide an egg. This was retrieved and fertilized by sperm from the daughter's husband in a culture dish. The resultant embryo was implanted in the mother who successfully gave birth to twins.

Surrogacy: If a woman has lost her uterus, another woman can provide hers for pregnancy and childbirth. This is somewhat different from the previous example, because the partner usually has intercourse with the other woman in order to impregnate her, and money is involved. The custody of some infants of surrogacy birth has been bitterly fought over in the law courts. Perhaps only in very close and loving families does surrogacy not prove to be a very tricky area of human choice.